1. Technical Field
The present invention generally relates to monitoring devices and, more particularly, to a tire monitoring device adapted to create an indication signal in response to an overheated tire condition. Specifically, the invention relates to a tire monitoring device having a sensor that is adapted to identify airborne molecules that are created when tire rubber becomes overheated.
2. Background Information
Various different tire monitoring devices are known in the art. The various monitoring devices are configured to sense different tire conditions such as tire pressure, temperature, revolutions, and footprint shape. One type of monitoring device is attached to the tire valve and is disposed outside the wheel. Another type of monitoring device is carried inside the wheel and may be attached to the tire or the rim. Another type of known tire monitoring device is loosely disposed within the wheel. A drawback to these devices is that it is difficult to configure them to create an early warning signal in response to the beginning of an overheated tire condition.
In some situations, a tire that is beginning to fail includes components that are frictionally moving with respect to each other. The friction generates heat that will raise the internal temperature of the tire. Overheated tire components break down and weaken the tire. Although monitoring devices configured to sense temperature will create a warning signal when the overheated tire condition has warmed the tire or the tire chamber to a certain level, they generally do not create a signal at the beginning of an overheated tire condition. Known tire monitoring devices will not create the warning signal at the beginning of an overheated tire condition when the temperature sensor of the monitoring device is not positioned close to the components that are creating the friction. With some prior art tire monitoring devices, the monitor will not generate an alarm signal until the overheated condition has warmed the area of the tire adjacent the temperature sensor or the internal chamber of the tire. Such warming takes time which allows the condition causing the overheating to worsen before it is detected. The art thus desires a monitoring device that is configured to sense the beginning of the overheated tire condition.
A current trend in the mining industry is a move towards unmanned trucks. With the precise level of control available through the current GPS systems and remote monitoring, it is possible to send equipment on hauls without the need for a human operator. Under this arrangement, the vehicle monitors various operating parameters of the on-board systems and periodically communicates the condition of on-board systems via radio to a central dispatch location. The monitored systems can include various temperatures, fluid levels, and pressures. Whenever any of these monitored parameters reach an out-of-limit level, corrective action can be taken immediately, for instance, directing the vehicle to an appropriate maintenance facility.
The performance of the tires must be closely monitored because the movement of the vehicle is dependent upon the tires. Typical mining applications involve operating the vehicles at the limits of designed load and operational capacity. Such conditions place the tires under continual stress. Tires not adequately inflated to the pressures required for these conditions may overheat and ultimately suffer a heat-related injury and early removal from service.
Tires that overheat generally begin to suffer damage as the polymer breaks down and loses structural integrity. As the polymer degrades, micro-fractures in the polymer chain begin to grow, resulting in larger cracks. These cracks then create friction that produces more heat and more damage. This process will continue and accelerate, resulting ultimately in the loss of structural integrity of the tire if the tire is not removed from service or placed in a less-severe operating environment.
These small pockets of micro fractures generate heat and can reach damaging levels of temperature causing breakdown of the polymer and other chemicals and additives in the rubber compound. Airborne chemicals are released and result in an odor often termed “burning rubber smell.” Many times, an overheated tire is identified first by this distinctive odor. Because these pockets of micro fractures are relatively small initially, the heat generated is insufficient to significantly raise the overall tire temperature or temperature of the contained air within the tire chamber. Therefore simple temperature detectors will not identify an overheated tire until the tire damage is relatively extreme.